ESSENTIAL TREMOR
Philip A. Hanna, M.D.
Parkinson's Disease and Movement Disorders Center
New Jersey Neuroscience Institute
Edison, New Jersey
Tremor is a rhythmical movement which is a result of involuntary
muscle contractions. Tremors are classified into two main categories
being rest and action tremors. The classic rest tremor is the
"pill-rolling" tremor of Parkinson's disease. Action tremors
are seen during voluntary muscle contractions, and may be further
divided into 1. postural tremors seen with anti-gravity postures such
as holding one's arms outstretched horizontally in front of them, 2.
kinetic tremors may be seen at the onset of voluntary movement
(initial tremor), during the movement (dynamic tremor) and upon
approaching the target (terminal tremor or intention tremor). Some
tremors occurs predominantly during certain tasks (primary handwriting
tremor) or speaking/singing (voice tremor) and thus are called
"task-specific" tremors. Certain tremors are
position-specific (while holding a telephone) and others are isometric
(voluntary contractions without change in position such as squeezing a
fist or while standing (orthostatic tremor).
The most common form of tremor is the postural tremor associated with
essential tremor (ET) sometimes called "benign essential
tremor" or "familial tremor". This form of tremor
affects at least 1% of the population and when severe may cause
notable functional limitation such as difficuly eating, drinking and
writing. While the cause of ET is unknown, there is strong evidence
for a genetic origin with at least two-thirds of patients having a
first-degree relative with tremor. Studies with large families have
yielded promising results with regards to locating gene loci relevant
to ET.
The majority of patients with ET note reduction of tremor with the use
of alcohol, yet regular use of alcohol is not advisable. Propranolol
(a beta-blocker) remains the most effective medication for ET, though
possible side effects include fatigue, depression and sexual
dysfunction and this agent is contraindicated in patients with asthma,
congestive heart failure and insulin-requiring diabetes. Primidone has
been shown to be effective in a number of clinical trials. Possible
side effects include nausea, sedation and an unsteady gait. Other
agents such as benzodiazepines may also be helpful. Gabapentin (Neurontin)
is being studied and has shown mixed results. The use of botulinum
toxin has also been used quite effectively for focal tremor. The
recent use of Deep Brain Stimulation has provided dramatic benefit to
a large number of patient who were refractory to other modalities.
International Tremor Foundation (ITF)
7046 W. 105th St.
Overland Park, KS 66212-1803
(913) 341-3880, Fax (913) 341-1296. Email: IntTremorFnd@worldnet.att.net
Hanna PA, Cardoso F, Jankovic J. Basal Ganglia and Movement Disorders.
In: Rolak LA, ed. Neurology Secrets, 2nd ed. New York: Hanley and
Belfus, 1998:137-169.
Higgins JJ, Jankovic J, Loveless LM, Patel P, Nee LE. Evidence that a
gene for essential tremor maps to chromosome 2p in four families. Mov
Disord 1998;13:972-977.
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